Dental color keys have been known for a long time. The color key according to U.S. Pat. No. 4,541,801 serves as an example. With a color key of this type, at least two different color patterns or samples with varying tooth colors are used and placed next to a neighboring tooth of the tooth to be restored. Each color sample typically has about the surface area of a tooth and often also has a curvature of its surface similar to a tooth.
Some more recent examples for dental color keys of this kind are solutions or approaches known from U.S. Pat. No. 5,653,589 and EP 1 002 502 A2. These solutions or approaches in fact represent improvements as the manageability of individual color patterns or samples and for this reason the possibility for the dentist to judge a color sample in relation to a natural tooth is improved. However, the result of comparison strongly depends on the subjective sensation or personal opinion of the dentist, and further for example also on the conditions of light exposure especially if a color sample of the color key is placed next to a tooth.
In particular the curvature of the color patterns or samples, which curvature is regarded as desired, requires a distinct three-dimensional design or configuration of the color patterns or samples such that a small color rod clearly projects even if it is placed or held next to a tooth. This already requires different light conditions as color sample and tooth then never are arranged on the same optical plane.
In order to exclude human influences on the judgement, it has been proposed to acquire an existing tooth color by use of a dental camera and to electronically select the suitable tooth color such as A2, A3 etc. For such a solution however it is necessary to perform complex calibration steps. An electronic color detection device of this kind is rather costly and therefore comes into consideration only with major dental practices.
The color keys known, purely for spatial reasons, typically merely comprise the most popular or established tooth colors that for example comprise no bleaching colors and even more no gingival colors.